1. Field of the Invention
The invention relates to a multiple gear transmission with magnetic control for vehicles or for use in drive technology with an input shaft supported on a frame and an output shaft, the input shaft and the output shaft protruding from the frame.
2. Discussion of Background Information
For the past 100 years it has been impossible to imagine the field of motorized vehicles without manual transmissions. They are also used in numerous machines in drive technology. These are very often transmission constructions that operate with the aid of gear wheels as a spur gear transmission or planetary gear train. However, the production engineering of these transmissions is generally very complex and expensive.
Since these power transmitting transmission components are generally made of steel, the weight is currently increasingly the focus of criticism and should be seen as a disadvantage. Lighter transmissions would reduce energy consumption, for example.
Ground vehicles, aircraft and watercraft should be seen by way of example here which may be equipped with internal combustion engines, electric motors or other units. Likewise a use in vehicles that are driven by muscular energy is conceivable. In order to guarantee easy propulsion, the vehicles must be extraordinarily light. The functional description of the transmission for this reason will provided using a bicycle by way of an illustrative example.
In the past forty years the chain drive with a shifting capability at the rear axle has become widely used with bicycles. To this end, a rotatable bottom bracket with one or more chain rings is mounted onto the frame which forms the load-bearing component of the bicycle with all its receiving points for the front wheel fork, the seat post and the rear wheel. A cassette comprising up to ten sprockets of different sizes is located on the hub of the rear wheel. At one dropout located directly at the rear axle a rear derailleur is installed, which has the task of guiding the chain in the sprockets of the cassette and to render possible shifting processes. Through a front derailleur that is usually installed at the seat tube it is possible to switch between the various chain rings at the bottom bracket. The capability of shifting allows the rider to adapt the gear ratio of his/her drive to the respective riding situation. Bicycles with a shifting system as described above are generally referred to as bicycles with derailleur gears.
As the components are mounted outside on the frame for constructional reasons with a bicycle with derailleur gears, the components are particularly exposed to environmental influences. Dirt and water thus come into contact with the rear derailleur, chain, cassette and other components in an unobstructed manner. This drastically reduces the efficiency of the derailleur gears, which is initially very good. For this reason, a considerable part of the force must be used to overcome the resistance within the shifting system.
In order to ensure functionality it is necessary to regularly service the components of the derailleur gears, which includes cleaning and greasing the components and adjusting them precisely. This adjustment can easily change, e.g., with falls or contact with objects (stones, branches, etc.). As tiny dirt particles always remain in the shifting system and in particular in the bearings even with the most intensive servicing, some parts need to be replaced regularly. In particular the parts susceptible to wear, such as chain rings and chain require an annual replacement, which in turn incurs additional expenses.
Shifting with derailleur gears is possible only with rotating sprockets, since otherwise the chain cannot be changed. It is therefore to be seen as a disadvantage that switching at stop is impossible due to the structural design. Furthermore, components can be damaged or torn off the frame with a fall or contact with stones or branches or other objects. The listed circumstances are to be seen as a disadvantage of derailleur gears.
Alternatively to the derailleur gears, the so-called “integral rear hub” was developed in which the shifting processes take place in a transmission in the rear wheel hub. The parts required with the derailleur gears, i.e., rear derailleur, front derailleur and cassette are thus omitted. Bicycles of this type are generally called bicycles with integral rear hub. An integral rear hub thus avoids the disadvantages of derailleur gears.
Because of the transmission integrated into the rear wheel hub, however, the weight of the rear wheel increases. In particular with so-called mountain bikes, which are moved off-road, an increase in mass at the rear wheel becomes highly noticeable. This applies in particular to bicycles with rear wheel suspension. The ratio of sprung to unsprung mass is of decisive importance for the riding behavior of a sprung wheel. The larger the unsprung mass is in relation to the sprung mass, the more critical is the riding behavior of the wheel. With high unsprung mass (heavy rear wheel) thrusts caused by road bumps cannot be compensated for in an optimum manner by the chassis.
With a known bicycle (cf. DE 103 39 207) the transmission is located within the bicycle frame. The bottom bracket shell of the classic bicycle frame is omitted and replaced by the transmission housing. This is a joint housing for the transmission and bottom bracket. Similar to the bicycles with the transmission hub, the power is transmitted to the rear wheel via a chain or a toothed belt, where the chain and the rear wheel hub do not have a shifting function with this system. The rear wheel hub can thus be built in a very light manner, which results in a more efficient rear wheel suspension. Furthermore, the center of gravity shifts to the center of the bicycle, directly below the rider, which results in a more agile and controlled riding behavior. In addition, the so-called “platform strategy” can be used with the aid of the transmission integrated into the frame.
It has been customary in bicycle construction to first build a frame and then to equip it with its components; however, the concept of the transmission integrated into the frame renders it possible for the first time to use the platform strategy known from automobile construction in bicycle production. For example components, such as the shifting system, suspension, the complete power transmission, brakes, generator and lighting are firmly installed in the transmission housing as a platform. The customer-specific parts, which complete the bicycle according to customer or manufacturer specification, are then mounted to the transmission thus equipped.
The transmission according to DE 103 39 207 comprises a planetary transmission and a primary drive. The primary drive is necessary because the planetary transmission developed for use in a transmission hub does not withstand the high torque acting in the bottom bracket. The primary drive brings the planetary transmission to a higher rotational speed, so that it can withstand the acting forces. This construction, however, lowers the efficiency of the drive. This is to be seen as a disadvantage.
Likewise similar transmissions are known, e.g., from U.S. Pat. No. 5,553,510, U.S. Pat. No. 4,955,247, U.S. Pat. No. 5,924,950, DE 2020178U1, WO 2006/039880 A1, US 2004/0067804 A1 and US 2004/0066017 A1. These designs are generally very heavy and complex. One of the shafts is generally the drive shaft and another shaft is the driven shaft. The drive shaft is also referred to below as the input shaft. The driven shaft is also referred to below as the output shaft. If only the term shaft is used below, either the input or the output shaft is meant.
A chain-drive transmission is known, e.g., from U.S. Pat. No. 4,158,316. In this transmission several sprockets with different diameters are rotatably mounted on the axle. The sprockets can be locked in a rotationally fixed manner to the shaft by a coupling and thus transmit a torque. The disadvantage of this lies in the high weight, in particular through the use of a steel chain, and through the large space required, the complexity of the couplings and the coupling control.
A similar chain-drive transmission is known, e.g., from US 2004/0067804 A1 and US 2004/0066017 A1. In these bicycle transmissions various drive wheels are mounted on the input shaft and output shaft, which wheels are connected in pairs to drive mechanisms. Different gear ratios are achieved in that a shifting component inside the drive shaft is axially displaced with the aid of a cable. A connection element on the shifting component engages in the desired drive wheel and generates a rotationally fixed connection between the driven shaft and the drive wheel. However, the described structure has disadvantages, which will be described in more detail below.
Both U.S. Publications, e.g., US 2004/0067804 A1 and US 2004/0066017 A1, disclose that the drive wheels are arranged next to one another such that they form the shape of a conical envelope. The shape of a conical envelope is formed when the diameter of the drive wheels increases from small to large on the shaft. This special feature of US 2004/0067804 A1 and US 2004/0066017 A1 is in fact to be regarded as a disadvantage:
Gear ratios on bicycles should increase speed in the range of 0.7-4.0. Considering the size of the sprocket wheels and their number of teeth in US2004/0067804 A1 and US2004/0066017 A1, this range of gear ratios will be difficult to achieve. Furthermore, considered in terms of sports biology, only gear steps of less than 15% can be handled well by a person.
The so-called secondary transmission is formed by two further belt wheels, which transfer the torque from the transmission to the rear wheel. It is advantageous if these belt wheels do not impair the function of the pedal bearings and the rear wheel hub by their proportions. The design according to US 2004/0067804 A1 and US 2004/0066017 A1 would make a very large and voluminous structure, if the framework conditions with respect to secondary transmission, overall transmission and gear transition were to be achieved.
Belt and chain drives in general have a discrete axial distance, which depends exclusively on the pitch and the length of the belt, and the diameter or the number of teeth of the belt wheels used. This axial distance can be described by the following formula:
  a  =            p      /      4        ⁢          ⌊              X        -                              (                                          z                1                            +                              z                2                                      )                    /          2                +                                                            [                                  X                  -                                                            (                                                                        z                          1                                                +                                                  z                          2                                                                    )                                        /                    2                                                  ]                            2                        -                                          8                ⁡                                  [                                                            (                                                                        z                          2                                                -                                                  z                          1                                                                    )                                        /                                          (                                              2                        ⁢                        π                                            )                                                        ]                                            2                                          ⌋      a=axial distancep=chain pitch of the chainX=number of links of the chainz1=number of teeth of the small sprocket wheelz2=Number of teeth of the large sprocket wheel
If this formula is applied to US 2004/0067804 A1 and US 2004/0066017 A1, it is found that not every individual belt wheel has the correct axial distance. A structure according to US 2004/0067804 A1 and US 2004/0066017 A1 is thus disadvantageous, since some chains are taut and others are loose. This must be considered a major disadvantage, since incorrectly tightened chains have excessive wear. This disadvantage is referred to below as “only discrete axial distances possible.” Only discrete axial distances are possible with U.S. Pat. No. 4,158,316 due to the belt used. This must also be seen as a disadvantage. At the same time, it should be noted that this disadvantage of the discrete axial distances also occurs with gear trains.
Another major disadvantage is to be found inside the shifting control with U.S. Pat. No. 4,158,316, US 2004/0067804 A1 and US 2004/0066017 A1. If a gear change is to be performed, first a belt wheel is disengaged from the driven shaft and only thereafter is another belt wheel engaged to the shaft. As a result, with these drives a permanent rotationally fixed connection between the shaft and a gear wheel is not guaranteed. During a change of gear, a neutral position can occur. To the cyclist this means suddenly pedaling “into a void.” This can cause injuries, particularly in the knee area.
In the past, belt and chain drives were often found with belts running parallel, in which the belt wheels are engaged to one axle (see also CH 167867, U.S. Pat. No. 6,146,296 and U.S. Pat. No. 5,871,412). However, all of these constructions exhibit the disadvantage that a small time window with a neutral position could always develop between two engaged gear ratios. In particular under load it cannot be ensured that a brief clutch slip cannot occur during this time window. Likewise a clutch slip of this type leads to enormous wear on the clutches. Over the long term damage cannot be excluded under certain circumstances.
To sum up, many transmissions according to the above systems have problems with respect to weight, production costs, ability to shift under load, neutral position and ability to switch at stop.